The phloroglucinol glucoside derivative [2,4-dihydroxy-6-(beta-D-glucopyranosyloxy)phenyl]-butan-1-one (1), roseoside (2), and kaempferol-3-O-beta-D-glucopyranoside (3) were isolated from the aerial parts of Conyza aegyptiaca (L.). To the best of our knowledge, this is the first isolation of compounds 1-3 from C. aegyptiaca. Their structures were determined by spectroscopic techniques including, IR, HR-EIMS, and extensive 500 MHz 1D- and 2D-NMR analyses (1H, 13C NMR, DEPT, 1H-1H COSY, HMQC and HMBC experiments). The antioxidant activity of 1, using the DPPH assay, was investigated; in addition, 1 was investigated against different types of cell lines, including Hep-G2, HCT-116, and RAW 264.7 for its cytotoxic effects. Also, this is the first report on the activity of 1.